Project Name

Rock Creek Fish Ladders

Fish Passage and Screening
Client / Agency
Marys River Watershed Council
City of Corvallis, US Forest Service, Oregon Watershed Enhancement Board
Corvallis, Oregon
2007 to 2008
Project Description
In 2006, the City of Corvallis adopted the Corvallis Forest Stewardship Plan (CFSP 2006) that outlined a strategic plan for managing and enhancing the Corvallis municipal watershed area. As part of the plan, it was recommended that Griffith Creek and South Fork Rock Creek water diversion dams be retrofitted with fish ladders to provide fish passage. The dams are owned and operated by the City of Corvallis and are located in the Corvallis Municipal Watershed west of Philomath. The Griffith Creek dam was built in 1983 using reinforced concrete with two 6 ft bays and a sediment sluice gate. The left bay had a stainless steel screen with perforations to allow water to run over the screen and drop through to a water intake structure. The screen is similar to the standard self-cleaning, Coanda screen regularly used at water intake structures except the intake structures utilize a stainless steel plate rather than screens. The right bay contains removable wood flashboards to control the overflow elevation of the impounded water and allows water to freely overflow onto a concrete apron at the bottom of the structure. The change in elevation between the minimum impounded water surface and the tailwater is approximately 5 ft. The existing dam had no fish passage facilities. The South Fork Rock Creek dam was a reinforced concrete structure built in 1983. The existing structure was reinforced concrete that contained four 6 ft bays and a sluice gate. The three left bays have stainless steel screens with perforations to allow water to run over the screen and drop into a water intake structure. The water intake screens are similar to the standard Coanda screen used at many water intake structures, but utilize a stainless steel perforated plate. The right bay contains several removable flashboards and an antiquated pool and weir fish ladder. The existing fish ladder does not meet current ODFW fish passage criteria primarily due to jump height exceeding 6 inches. The dam has a concrete apron at the tailwater location and a sluice gate on the left side of the dam for cleaning out fine sediment upstream of the dam.
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Retrofit concrete fish ladder installed on the Griffith Creek water intake structure for the City of Corvallis.